The technique operates on the idea lipids in the bilayer of a cell’s plasma membrane block visible light. This is why the brain is normally not transparent. Removing these lipids but still keeping the other parts of the cell and its environment intact would render the brain “see-through” and allow for much easier imaging of large pieces of brain tissue, if not the whole brain at once. This idea is carried out by taking the brain and infusing it with acrylamide, which binds proteins, nucleic acids and other molecules, then heating the tissue to form a mesh that holds the tissue together. The brain is then treated with SDS detergent to remove the light-blocking lipids resulting in a stable brain-hydrogel hybrid. From here the transparent tissue can be fluorescently labeled for certain cells and analyzed. Through the whole process there is less than 10% protein loss in the brain tissue compared to around 41% for other current methods. This is an amazing improvement!

Example of brain image produced by CLARITY from neurons in an intact mouse hippocampus. (http://med.stanford.edu/ism/2013/downloads/CLARITY/CLARITY_stained.jpg)

Until now it has been common practice to use histology to analyze brain tissue in a study. This method involves slicing a section of brain up into extremely small pieces and dying certain slices for various cells and molecules of interest. If a researcher wants any idea of the bigger picture he/she must reconstruct the brain from these small slices. With the CLARITY technique slicing the brain up is no longer necessary. Never before has it been so easy to view full brains, or sections of brain, down to the cellular and molecular level. It is now easy to follow the trajectory of a single neuron through the whole brain.

The development of this brain imaging method comes at a time when much money is being put into uncovering the complete biological workings of the human brain. President Obama has announced his BRAIN initiative and the US National Institute of Health is working on its Human Connectome Project. CLARITY has big potential use for these initiatives and as the technique is refined it seems that it will have a large role in uncovering more about the elusive question of how our brains really work.

For more information on CLARITY view this video on Nature’s website:

http://www.nature.com/news/see-through-brains-clarify-connections-1.12768

- J. Daniel Bireley

Sources:

Structural and molecular interrogation of intact biological systems – Nature

See Through Brains Clarify Connections – Nature

At his State of the Union address nearly two months ago, President Obama announced plans for the Brain Activity Map (BAM) project (see The Nerve blog Part 1 and Part 2), a billion-dollar ten-year research initiative to gain a better understanding of the brain and to provide deeper insights into diseases like Alzheimer Disease, Parkinson Disease, and Autism Spectrum Disorder.

On Tuesday, April 2^nd, the President announced that he plans to include the BAM project – now termed the BRAIN (Brain Research through Advancing Innovative Neurotechnologies) Initiative – in his 2014 budget proposal. The director of the NIH, Dr. Francis Collins, notes that one of the major goals of the project is to simultaneously sample from many neurons in real-time. Although existing technology can measure the activities of single neurons and of brain regions, it cannot measure those of circuits. Because existing technology has not yet advanced to a level that allows such complex analysis, the BRAIN initiative will be initially funded $100 million for the year of 2014 to develop and advance neuroscience technologies. Yearly negotiations will take place to determine future funding.

Over the next several months, 14 leading neuroscientists from Stanford, CIT, Harvard, Brown, Princeton, and Brandeis will serve on the advisory board (also called the “dream team” or the “brain trust”) to refine the project’s immediate and long-term goals. They will need to decide which research areas are of high priority, which projects require more funding, and which technologies need to be developed and employed. Additionally, President Obama has required a study to explore the ethical, societal, and legal problems associated with the project’s advances in neuroscience.

Dr. Francis Collins and President Obama on Tuesday, April 4th at the White House

Although $100 million may not be sufficient to transform neuroscience, it may “help get this project off the ground,” as President Obama says, and forge a new path for advancing neuroscience. In fact, Francis Collins notes that the Human Genome project was only funded $28 million for its first year. Further, private organizations including the Allen Institute for Brain Science, the Salk Institute for Biological Studies, the Howard Hughes Medical Institute, and the Kavli Foundation have already committed $158 million.

Just as genetics research had been underway before the Human Genome Project, neuroscience research has been going on long before the announcement of the BAM project or the BRAIN initiative. Hopefully, this investment in neuroscience research will do for neuroscience the same that the Human Genome Project did for genetics: provide a plan considering the state of current research, speed up the process of improving the state of knowledge, bring more money into the economy than funded, recruit additional experts to foster an interdisciplinary effort, and capture the interest of the general public. The BRAIN Initiative should provide a goal-oriented long-term focus and allow the coordination and collaboration of neuroscientists in advancing biology, health, medicine, and society.

“Of course, none of this will be easy. If it was, we would already know everything there was about how the brain works, and presumably my life would be simpler here. It could explain all kinds of things that go on in Washington.” – President Obama

-Margaret McGuinness

Sources:

Eve Marder joins Obama neuroscience ‘brain trust’ – BrandeisNOW

Obama outlines private-public project to study the brain – Los Angeles Times

Neuroscience: Making connections – Nature

Obama to Unveil Initiative to Map the Human Brain – New York Times

BRAIN Initiative – NIH

A Brief History of the Human Genome Project – NIH NHGRI

Researchers Question Obama’s Motives for Brain Initiative – NPR: Morning Edition

President Obama Calls For A ‘BRAIN Initiative’ – NPR: Talk of the Nation

BRAIN Initiative Challenges Researchers to Unlock Mysteries of Human Mind – The White House Blog

Fact Sheet: BRAIN Initiative – The White House: Statements and Releases

“Man had always assumed that he was more intelligent than dolphins because he had achieved so much — the wheel, New York, wars and so on — whilst all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man — for precisely the same reasons….In fact there was only one species on the planet more intelligent than dolphins, and they spent a lot of their time in behavioural research laboratories running round inside wheels and conducting frighteningly elegant and subtle experiments on man. The fact that once again man completely misinterpreted this relationship was entirely according to these creatures’ plans.” – Douglas Adams, The Hitchhiker’s Guide to the Galaxy

As tempting as it may be to believe the science fiction version of the intelligence rankings, real-life science has spoken and suggests (much to my displeasure) that humans may actually be the highest on the intelligence scale.

Glia are non-neuronal cells found in the brain mainly described as performing “housekeeping” functions, for example, providing structural support to neurons, and providing them with nutrients. Astrocytes are a specific type of glia, and as one might hypothesize, they are bigger in humans than in mice. Was this just a consequence of humans having more complex brains, or do these astrocytes have different functions in humans beyond the basic housekeeping functions? To test this, scientists grafted human astrocyte progenitor cells into developing mouse brains to create chimeric mice.

Human astrocyte (green) and mouse astrocyte (red)

The human astrocytes that matured successfully matured as human cells; characteristics such as their size were unaffected by being in a mouse environment. But they did not remain completely foreign – they successfully formed electrical connections with the mouse cells. Their differing cellular properties were thus propagated into the mouse neural networks. Of particular interest is the hippocampus, the brain region important for learning and memory. Chimeric hippocampal slices had a higher level of baseline excitatory activity, and long-term potentiation (LTP), or synapse strengthening, was much greater. At the molecular level, this can be explained because the human cells express higher levels of a protein that promotes an increased number of glutamate receptors at the synapse.

There were also clear differences in the behavior of chimeric mice. Experiments were performed to test learning and memory abilities to corroborate the cellular results observed in the hippocampus. A classic fear conditioning experiment involves pairing a tone with a foot shock; mice learn to associate the two and exhibit freezing behavior after hearing a tone. Chimeras learned the association after only one tone/shock pairing. The learning persisted for several days, during which time control animals did not learn the initial association. The experiment was repeated as context fear conditioning, meaning that the mice were placed in different chambers that had varying floors and odors. Chimeric mice were able to differentiate between chambers significantly better than their control counterparts. In other learning and memory tasks, these mice learned their way through mazes faster and were better at familiar object recognition in novel contexts.

The results of this study show that glial cells have much more function beyond their basic housekeeping properties. A single cell graft manipulation was enough to significantly improve mouse performance on learning and memory tasks. Complexity of these cells has evolved with the brain, and this provides important new insight on how exactly this complexity has come to be. Future experiments could involve grafting chimpanzee or macaque glia, any differences observed could be key in outlining how our processing abilities evolved from our monkey fathers (I additionally support research with dolphin glia grafts, keeping on the theme of the three most intelligent species). Unfortunately, without the higher processing abilities made possible by human cells, mice likely cannot achieve the tasks and level of status they exhibit in the science fiction. It seems as though man has indeed correctly interpreted his relationship with the mouse.

So long, and thanks for all the fish.

-Reena Clements

References:

Human Brain Cells Boost Mouse Memory – ScienceNOW

Forebrain Engraftment by Human Glial Progenitor Cells Enhances Synaptic Plasticity and Learning in Adult Mice – Cell Stem Cell

In the past 150 years it has been noted that the onset of depression is occurring at higher rates and at younger ages that ever before. This data could be the result of factors including an increase in patients coming forward to be diagnosed, improved diagnoses, or simply better record keeping. Whatever the reason, it is estimated that 15 to 20% of the population is experiencing symptoms of major depression at any given time, with a greater occurrence in women than in men. Many are affected by this disorder and a cure has yet to be found. But before we continue, a distinction must be made between major depression and “reactive depression” in which a person may feel depressive symptoms because of a single event like the loss of a loved one or a failure of some kind. Major depression is a prolonged state in which an individual may display a number of symptoms including depressed mood, loss of interest in most activity, change in body weight or appetite, changes in sleep patterns, psychomotor agitation or retardation, fatigue, difficulty concentrating, feelings of worthlessness or guilt, and suicidal thoughts. Depending on the severity of the depression a patient may display many, or only a few of these possible symptoms.

Research has yet to find a definitive neurological cause for depression and other affective disorders. Studies of fraternal and identical twins have attempted to determine the role of nature versus nurture on the matter and animal models of depression as well as human studies have been used to develop drugs and other treatments for depression. Through this work different hypotheses have developed about the neurochemical basis of depression. Some are convinced a monoamine imbalance is responsible while others say it is an issue with serotonin dysfunction. These hypotheses have led to the development of different treatment methods and the utilization of a few classes of drugs. Drug classes include monoamine oxidase inhibitors, tricyclics, and selective serotonin reuptake inhibitors (SSRIs) which all have slightly different mechanisms of action in the brain when treating depression. What is most interesting is that after all this research and development none of these drugs stand out as the best treatment for depression. They all tend to improve depressive symptoms anywhere from a week to a month after drug therapy begins, and they all carry different, sometimes nasty, side effects. The main reason for the current love affair with SSRIs in the medical world is that they carry the most favorable set of undesirable side effects, not that they treat depression best.

Enter ketamine. This compound has a street reputation as a club drug and is derived from phenylcyclidine (PCP), another drug known for its powerful and potentially dangerous psychological and addictive affects. Both drugs were originally developed as alternative analgesics (pain relievers) to drugs like barbiturates that had a higher risk of respiratory depression and subsequent death. PCP and ketamine did produce analgesia, just not in the way they were originally thought to do so. Patients report feelings of detachment from their own body and reality when under the influence of these drugs. They can’t feel pain because their minds are off in another reality, essentially too distracted to feel anything. At high doses PCP and ketamine have been shown to induce schizophrenic symptoms in humans, or worsen previously existing schizophrenia, and research on schizophrenia uses ketamine to bring about a schizophrenic state in animal test subjects. So how on earth can a drug like this have any useful therapeutic application?

http://drug-effects.us/what-is-ketamine

http://www.guardian.co.uk/society/2010/apr/02/drugs-ketamine-bladder-problems-incontinence

Researchers at Yale University and the National Institute of Mental Health have recently found that administering a low dose of ketamine to a patient affected by major depression has been able to lift the patient’s mood and subdue the depression for about a week at a time. It is an astounding find given the known effects of ketamine on the mind. One study reported that 70% of patients treated with ketamine experienced an improvement in mood. One of the best parts about the treatment is that it takes effect immediately, unlike the other antidepressants on the market, which can take up to a month to work. It has also proven effective even to patients who have been resistant to other treatments. Ketamine is already an FDA-approved analgesic, usually used in veterinary settings, so further studies of this compound are now being developed in humans.

The mechanism of action for this drug is not yet clear but it is known that ketamine and PCP are nonselective NMDA receptor antagonists. They affect the glutamate pathways within the brain and also seem to have the remarkable affect of strengthening and restoring synaptic connections. In the human model of depression where it is thought that symptoms are caused by atrophy of neurons in various brain areas, it makes sense that ketamine is an affective treatment because it encourages neuron regrowth and connection. This may be done through the production of brain derived neurotrophic factor (BDNF) or other molecules that influence neuron health and maintenance. More work must be done to determine how this unlikely drug accomplishes its therapeutic affects. There are still dangers associated with taking ketamine, especially if it only works for a week at a time to treat depression and repeated use has already been shown to produce schizophrenic symptoms in some. It is an amazing and surprising find and hopefully it leads to more improved treatments of affective disorders like depression.

- J. Daniel Bireley

Sources:

Ketamine Relieves Depression By Restoring Brain Connections – NPR

Signaling pathways underlying the pathophysiology and treatment of depression: novel mechanisms for rapid-acting agents - Trends in Neurosciences

Meyer, Jerrold S., and Linda F. Quenzer. Psychopharmacology: Drugs, the Brain, and Behavior. Sunderland: Sinauer Associates, 2005. Print.